<html>
<head>
<script>
function showUser(str)
{
     if (str=="")
     {
           document.getElementById("txtHint").innerHTML="";
           return;
     } 
    if (window.XMLHttpRequest)
    {
           // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
           xmlhttp=new XMLHttpRequest();
     }
     else
     {
           // IE6, IE5 浏览器执行代码
           xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
     }
     xmlhttp.onreadystatechange=function()
     {
          if (xmlhttp.readyState==4 && xmlhttp.status==200)
          {
                document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
          }
     }
     xmlhttp.open("GET","getuser.php?q="+str,true);
     xmlhttp.send();
}
</script>
</head>
<body>
<form>
<select name="users" onchange="showUser(this.value)">
<option value="">Select a person:</option>
<option value="1">Peter Griffin</option>
<option value="2">Lois Griffin</option>
<option value="3">Glenn Quagmire</option>
<option value="4">Joseph Swanson</option>
</select>
</form>
<br>
<div id="txtHint"><b>Person info will be listed here.</b></div>
</body>
</html>